Introduce fastime.Since method (#47)

fastime_test.go

@@ -2,6 +2,7 @@ package fastime
 
 import (
 	"context"
+	"math"
 	"reflect"
 	"sync/atomic"
 	"testing"
@@ -398,3 +399,28 @@ func TestFastime_store(t *testing.T) {
 		})
 	}
 }
+
+func TestFastime_Since(t *testing.T) {
+	tests := []struct {
+		name string
+	}{
+		{
+			name: "since",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			now := Now()
+			timeNow := time.Now()
+			time.Sleep(100 * time.Millisecond)
+			since1 := Since(now)
+			since2 := time.Since(timeNow)
+			if since1 < 50*time.Millisecond {
+				t.Error("since is not correct")
+			}
+			if math.Abs(float64(since1-since2)) > float64(50*time.Millisecond) {
+				t.Error("since error is too large")
+			}
+		})
+	}
+}

global.go

@@ -44,6 +44,12 @@ func Now() time.Time {
 	return instance.Now()
 }
 
+// Since returns the time elapsed since t.
+// It is shorthand for fastime.Now().Sub(t).
+func Since(t time.Time) time.Duration {
+	return instance.Now().Sub(t)
+}
+
 // Stop stops stopping time refresh daemon
 func Stop() {
 	instance.Stop()